Manufacture of acoustic fireproof tiles



United States Patent r 2,934,789 MANUFACTURE or ACOUSTIC FIREPROOF TILESHenry William Heine, Washington, D.C.

No Drawing. Application September 3, 1958 Serial No. 758,867

2 Claims. (Cl. 18-475) This invention relates to the manufacture ofceramic tile. having the acoustic property of high sound absorption.

More specifically, this application is a continuation in part of myPatent No. 2,877,532 filed September 13, 1957, which in turn is acontinuation of my abandoned application Serial No. 324,852 filedDecember 8, 1952, each describing and claiming an acoustic tile as aproduct and its method of manufacture.

The overall purposes of this invention are: that the tile be capable ofwithstanding sufficiently high temperatures to answer fireproofingrequirements; that the tile have suflicient compression and tensilestrengths to withstand handling and the customary service requirements;and finally, that the materials used for the tile be plentiful andinherently lend themselves to the manufacture of ceramic acoustic tilewith the foregoing properties.

It is a further objective of this invention that the method ofmanufacture be such that acoustic ceramic tile with the properties Ihave above defined be relatively inexpensive to manufacture.

In my Patent 2,877,532, issued March 17, 1959 I define as my invention aceramic fireproof tile having a crumbly porous core which is light inweight, economical to manufacture pursuant to the method defined andmaterials used, and is without treatment for imparting mechanicalstrength thereto; said core having a protective envelope 1 adapted toprovide mechanical strength for handling the tile, which consists inglaze surface coverings with open pores communicating'with pores in thecore.

r In my copending application Serial No. 683,687 the specific method forthe manufacture of fireproof acoustic tile-of the type above definedwithout treatment for imparting mechanical strength to said core,consists, first in preparing a mix comprising 13 to 30 parts of ceramicma- :terials'ie, approximately 70% diatomaceous earth and 30% clay, thelatter preferably containing a natural glazing frit, of a known amount,then adding 7 to 30 parts mixwhich is followed by shaping the tile corestherefrom. The final step is to subject the tile forms to a kiln ,oroven temperature between 1900 and 2300" F., the

maximum temperature being reached as quickly as possible and maintainedbetween 1 /2 to 3 /2 hours. These steps of manufacture will produce fromthe materials employed the fireproof acoustic tile with the propertiesand structural features set forth in the preceding paragraph.

With the, present invention the steps are broadly the same as in mypending application Serial No. 683,687.

I also employ the same ceramic materials i.e., approximately 70%diatomaceous earth and 30% clay. Respecting the carbonaceous materialfor the mix I employ about the maximum stated for the mix in mycopending application for purposes which will later appear. The timeperiod for heat treatment is also about the same i.e., 1 /2 to 3% hours.Also, the maximum temperature range for heat treatment of the tile corein an oven or kiln is about the same as with my application i.e., be-

tween 1700" and 2300 F.

For the glazing of the tile with perforations communicating with theporous core, I depend on the salts brought to the surfaces of the coresduring the heat treatment by the steam and gases resulting from thewater and sawdust in the mix through the pores previously made by steamand gases from the same sources. The salts are derived from the mineralimpurities of the ceramic materials constituting the mix from which thetile cores are made, plus the addition of a soluble mineral saltincluding a vanadium salt, which are introduced into the cores throughthe water used for the mix.

For the protective covering of the porous crumbly tile core, in thepresent invention I depend upon the salts resulting from the mineralimpurities in the ceramic materialsused for the mix, plus the additionof a soluble mineral salt, and a small amount of vanadium salt. Morespecifically, the vitrified salts used for the protective core coveringin the present invention is the equivalent of fused salts such asdelivered by efiiorescence action to the surface of bricks after beingmanufactured. With bricks the manufacturer sometimes employe additivesto the mix for negativing efllorescence action while I do the reversei.e., increase the delivery of mineral salts by adding a soluble salt tothe tile core mix including a vanadium salt, and then through acontinuously rising kiln temperature increase continuously thesolubility of most of the salts in the mix at a rate. at times greaterthan that of the temperature rise. These rates can be compared byobserving the salts being delivered to the core surfaces by the steamand gases generated from the water and sawdust within the core throughpores previously formed by steam and gases from the same sources.

I find that with the higher kiln temperatures, say between l000 to 1200F. the increase of salts being delivered tis uniform but that thereafterthere are gaps in which the delivery is considerably lowered, if notstopped altogether. It is in these higher ranges of temperature Ibelieve the vanadium salts added to the mix serves to increase the saltsdelivered to the core surfaces over a certain temperature range. Forexample, when a calcium salt was added to the mixwith the vanadium saltthe greatest delivery of salts to the core surfaces occurred in thetemperature range between 1100 and 1300 F., while when an aluminum saltwas added with a vanadium salt the maximum delivery of salts to thesurfaces of the tile core cocurred over the temperature range of l400 to1700 F.

Diatomaceous earth is known to be a silicate of organic origin anddeposits occur in various regions of the earth as the skeletal residuesof certain forms of aquatic animal life. -It is characterized in onerespect by the fact that the skeletal structures of these animals,called diatoms, are essentially siliceous rather than calcareous as inthe case of other forms of animal life. It is also characterized by thefact that the skeletal structures of diatoms are multiformed, that issome of them are filimental, some are circular or oval, some are starshaped, some are tubular or drum shaped and still others are ofnon-descriptive or non-geometrical shapes. The particles are essentiallyhoL low and of graduated microscopic size. They have no definitecleavage planes as in the case of mineral silicates such as the variousforms of quartz or tridymite. The diversified forms of diatomaceousearth particles may be compared somewhat to snow and which in thenatural state is fluffy by virtue of different crystalline forms. Indiatomaceous earth the property of fluffiness is inherent due to thepresence of the diiferentskeletal forms and acting in this respectessentially as snow crystals and differing from other forms of mineralsilicates in much the same manner as snow differs from flakes of ice, Byvirtue of-this in? herent property and the hollow structureof-the'skeletal particles, diatomaceous earth has inherent porosity andthe ability to become fluffy; it is plentiful, and itlends itself to themanufacture of the acoustic tile with the properties heretofore defined.

The impurities in diatomaceous earth and clay constituting the ceramicmaterials I employ for producing tile of this invention contain avariety of minerals such as potassium, sodium, calcium, magnesium andaluminum. It is my belief that during the kiln treatment'of the tilecore the burning of the carbonaceous material produces soluble sulfatecompounds from the minerals in the ceramic materials employed, includingthose added, and thus provide white salt deposits on the surfaces of thetile. However, the vanadium salt when used will sometimes cause a slightgreen tinge in the covering of the tile core.

During the kiln treatment the salt deposit starts when the heat issufficient to convert water in the core to steam. The steam makeschannels or pores through the core and escapes; it carries to the coresurfaces the soluble salts. These salt deposits begin at about 250 F.and continue as the kiln temperature rises.

At this point it should be noted that I employ a good amount ofcarbonaceous material (sawdust) in order to hold as much water in thecore as possible during the higher kiln temperatures. Keeping water inthe sawdust during the higher temperatures is further helped by the factthat the inner part of the core maintains a lower temperature than thecrust thereof. This lower temperature is also produced by the fact thatthe tile cores are placed on pallets in the kiln and one face protectedfrom the heat to a certain extent. -But little glazing salts come tothis protected surface of the tile cores, however, the inner part of thecores near this protected surface remains soft and moist during thehigher kiln temperatures. This wet or moist sawdust permits thegeneration of steam to bring soluble salts to the surfaces of the corewith kiln temperatures as high as 1700 F. except from 1100" up to 1700the steam is intermingled with the gases from the burning of the sawdustbeginning with the particles nearest the surface of the core andgradually working inwardly until all the sawdust is consumed and allsoluble salt has been delivered to the core surfaces by the combinedaction of the steam and gases. Thereafter between 1900 and 2300 F. thesalts vitrify and a tough porous covering is had for the tile ofsufficient mechanical strength to withstand handling and to withstandthe stresses and strains to which acoustic tile as provided by thisinvention are customarily subjected.

A tile manufactured pursuant to my invention has very high soundabsorption. By closing the surface pores with a suitable glaze the tilebecomes an excellentinsulator to heat. This is because uncountableintercommunicating pores or channels, and cavities provide air chambersor passages which serve as heat insulation to the extentthat a torchapplied on one side of the tile produces little heat on the other side.Briefly, by brushing or spraying the tile surfaces with glazing materialsufficient to fully close the surface pores of the tile and thentreating the tile to heat for fusing or vitrification of the glazematerial provides a tile for heat insulation but not sound absorption.

Soluble salts of a number of other minerals than named above may be usedfor supplementing the salts derived from the ceramic materials used forthe tile core mix. Some of the minerals are barium, iron, zinc, tin,chrome, cobalt and lead.

In proportional amounts-a mix may consist of 15 to 30 .parts of ceramicmaterials, about 20 to 30 parts of sawdust; a supplement of about 1% to2 /2 parts of soluble salts including a soluble vanadium salt, and 40 to70 parts of water. Good results have been obtained by using a mixture ofabout 70% of diatomaceous earth and 30% of clay for the ceramicmaterials and about of a soluble calcium salt, and 20% of a solublevanadium salt for supplemental salts. The same percentages were used forthe supplemental salts when a soluble aluminum salt was substituted forthe calcium salt. The amount of water used should be such as is best forshaping the tile cores from the plastic mass i.e., all the water the mixwill take and still provide core forms which will hold their shape.Various clays may be. used for the mix, such as potters clay, fire clay,kaolin, etc., or mixtures thereof.

My process ormethod of manufacture essentially consists of threeprocedures, the first being to prepare the plastic mix from thematerials I have heretofore specified with water; the second being toshape the tile cores from the plastic mass; and thethird being .tosubject the cores to a one heat treatment for producing the finishedtile.

Any suitable equipment may be used for shaping the tile cores. The kilnshould have suitable pallets on which the tile cores may be placed. Thetemperature of the kiln should be raised as quickly as possible to thetemperature necessary for fluxing or vitrifying the salts deposited onthe surface of the cores during the heat treatment. The maximum heat isdependent upon the particular soluble salts deposited on the coresurfaces including the soluble vanadium salt. I have found thisvitrifying temperature is between 1700 and 2300 F. It is important thatthe heat be cut off from the kiln and cooling started as soon as thefusing or vitrifying of the salts takes place because if the temperatureis permitted to rise above the fusing of the salts the perforations inthe glaze formed may be closed, or partially so.

I claim:

1. A method for the manufacture of tile with a crumbly porous core and aglaze covering having a multiplicity of surface pores in register withpores in the core, which consists first in preparing a wet-mix ofceramic materials, burn-out materials, and water soluble mineral saltscapable of migrating to the surface of the core when subjected to firingtemperatures, next shaping tile cores from the mix, and finallysubjecting the core to a firing temperature from l700 to 2300 F. between1%. to 3 /2 hours whereby steam from the water in the mix provides poresextending from the tile core through the glaze covering thereof; theceramic materials in the mix being 13 to 30 parts of diatomaceous earth,7 to 30 parts of sawdust, 40 to 70 parts of water, and 1 A to 2 /2 partsof water soluble salts of which about 20% is vanadium salt which in turnco-acts with the other salts to accelerate the solubility thereof duringthe firing of the core to produce the glaze covering.

2. A method for the manufacture of a ceramic product with a crumblyporous core, and a glaze cov'eringhaving a multiplicity of surface poresin register with pores in the core, which consists, first in preparing awet-mix of ceramic materials, burn-out materials having the property ofwater absorption, and water soluble mineral salts capable of migratingto the surface of the core toprovide the glaze covering therefor whensaid core is subjected to firing temperatures, next shaping aproductcore from the mix, and finally subjecting the core to a' firingtemperature from 1700 to 2300 F. between 1 /2 to 3 hours whereby steamfrom the waterin each core provides pores extending from said corethrough the glaze covering thereof; the ceramic materials in the being13 to 30 parts of diatomaceous earth, 7 to 30 parts of burn-outmaterials, 40 to 7-0 parts of water, and 1%, to 2 4: parts of watersoluble salts of which about 20% is a vanadium salt whereby thesolubility of the mineral salts is increased during the highertemperature of core firing for producing the glaze covering.

(References 011' following page) References Cited in the file of thispatent 1,999,371 Parsons Apr. 30, 1935 2,124,086 Slidell July 19, 1938UNITED STATES PATENTS 2,241,705 Goodrich May 13, 1941 Husain et a1 Feb.14, 1933 2,552,553 Heine May 15, 1951 Heine Mar. 17, 1959 1,897,6671,941,403 Lansing et a1 Dec. 26, 1933 5 2,877,532

1. A METHOD FOR THE MANUFACTURE OF TILE WITH A CRUMBLY POROUS CORE AND AGLAZE COVERING HAVING A MULTIPLICITY OF SURFACE PORES IN REGISTER WITHPORES IN THE CORE, WHICH CONSISTS FIRST IN PREPARING A WET-MIX OFCERAMIC MATERIALS, BURN-OUT MATERIALS, AND WATER SOLUBLE MINERAL SALTSCAPABLE OF MIGRATING TO THE SURFACE OF THE CORE WHEN SUBJECTED TO FIRINGTEMPERATURES, NEXT SHAPING TILE CORES FROM THE MIX, AND FINALLYSUBJECTING THE CORE TO A FIRING TEMPERATURE FROM 1700* TO 2300*F.BETWEEN 1 1/2 TO 3 1/2 HOURS WHEREBY STEAM FROM THE WATER IN THE MIXPROVIDES PORES EXTENDING FROM THE TILE CORE THROUGH THE GLAZE COVERINGTHEREOF, THE CERAMIC MATERIALS IN THE MIX BEING 13 TO 30 PARTS OFDIATOMACEOUS EARTH, 7 TO 30 PARTS OF SAWDUST, 40 TO 70 PARTS OF WATER,AND 1 1/4 TO 2 1/2 PARTS OF WATER SOLUBLE SALTS OF WHICH ABOUT 20% ISVANADIUM SALT WHICH IN TURN CO-ACTS WITH THE OTHER SALTS TO ACCELERATETHE SOLUBILITY THEREOF DURING THE FIRING OF THE CORE TO PRODUCE THEGLAZE COVERING.